FIG. 1 shows radio resource control (RRC) service states 100 of a Third Generation Partnership Project (3GPP) wireless transmit/receive unit (WTRU) with an enhanced uplink in a Universal Mobile Telecommunications System (UMTS). The WTRU may operate in several states depending on user activity. The following states have been defined for UMTS Terrestrial Radio Access (UTRA) radio resource control (RRC) connected mode: IDLE 110, CELL_DCH 120, CELL_FACH 130, URA_PCH 140, and CELL_PCH 150. Other states that the WTRU may transition to include a general packet radio service (GPRS) packet transfer mode 160, a global system for mobile communications (GSM) connected mode 170, or an enhanced UTRA (E-UTRA) connected mode 180. RRC state transitions may be controlled by the network using radio network controller (RNC) parameters.
As part of the work effort for 3GPP Release 8, it has been proposed to allow a WTRU that is in the CELL_FACH state or in idle mode to use an enhanced random access channel (E-RACH) mechanism, whereby the WTRU uses enhanced dedicated channel (E-DCH) resources in the uplink (UL). The E-DCH resources are taken from a small pool of common resources that are shared among other 3GPP Release 8 CELL_FACH WTRUs. These WTRUs request E-DCH resources using the legacy random access channel (RACH) ramp up procedure. As part of this ramp up procedure, the WTRU transmits a randomly selected signature sequence, or a preamble signature, in a randomly selected access slot. If the signature is correctly decoded, a Node-B responds with an E-DCH resource assignment from its pool of resources, and the details are signaled to the WTRUs through the broadcast system information. In assigning the E-DCH resource, the Node-B needs only signal an index as to which E-DCH resource to use. The index is signaled over an acquisition indicator channel (AICH) or over an evolved AICH (E-AICH). Upon reception of the E-DCH resource index, the WTRU is configured with the E-DCH resource and may start transmitting UL data over the E-DCH.
A common E-DCH resource may be used by WTRUs that are in idle mode, CELL_FACH state, CELL_PCH state, or URA_PCH state. A WTRU in the CELL_FACH state may transmit common control channel (CCCH) traffic or dedicated control channel/dedicated traffic channel (DCCH/DTCH) traffic over the common E-DCH resource. If the WTRU has an E-DCH radio network temporary identifier (E-RNTI) allocated, the DCCH/DTCH data transmission over an assigned E-DCH resource starts with a contention resolution phase. During the contention resolution phase, the WTRU's E-RNTI is included in all the medium access control (MAC)-i protocol data units (PDUs). With the reception of the WTRU's E-RNTI, the network (e.g., Universal Mobile Telecommunications System Terrestrial Radio Access Network or UTRAN) is informed of which WTRU was granted the E-DCH resource and the Node-B may send an enhanced access grant channel (E-AGCH) signal confirming the WTRU's E-RNTI (through an E-RNTI specific cyclic redundancy check (CRC) attachment). If the WTRU does not receive its E-RNTI on the E-AGCH upon the expiration of a timer, then the contention has not been resolved and the WTRU releases the associated E-DCH resources.
If the WTRU has CCCH data to transmit, no contention resolution phase is performed. The WTRU has a maximum CCCH allocation time to transmit the data. When the time expires the resources are released.
The E-DCH resources may also be released due to the reception of the value “inactive” on E-AGCH; due to a radio link failure; due to total E-DCH buffer status (TEBS) equal to zero; or due to the expiration of an inactivity timer.
When a WTRU transmits CCCH traffic, the underlying assumption is that it will not have an allocated E-RNTI and will not perform contention resolution. Although this is the case for CELL UPDATE messages after a cell selection/reselection and for RRC CONNECTION REQUEST messages, situations exist where a WTRU has an E-RNTI and must transmit the CCCH traffic (e.g., a periodic cell update message). For such cases, WTRU behavior becomes ambiguous. According to current specifications, if an E-RNTI is allocated, the WTRU is required to add its E-RNTI to all MAC-i PDUs until the contention resolution is resolved (i.e., when the WTRU receives an E-AGCH with its E-RNTI). However, a WTRU that is transmitting CCCH traffic is not required to perform contention resolution and is not required to monitor the E-AGCH. Contention resolution may not be required for CCCH traffic, such as a periodic cell update message, since the periodic cell update message is anticipated to be small in size. Based on this assumption, on the network side, it is specified that when the WTRU E-RNTI is present, it identifies DCCH/DTCH data transmission from this WTRU, however, this assumption may not be correct, especially when an E-RNTI is present with CCCH data transmission.
Methods to handle the above described scenario are not defined and apparent. More specifically, the WTRU needs to handle the situation where a WTRU has common E-DCH resources allocated and is already sending DCCH/DTCH traffic when a periodic cell update is triggered. The WTRU also needs to handle the situation where a WTRU is already transmitting CCCH traffic with an E-RNTI allocated when DCCH/DTCH data becomes available for transmission.